Ophthalmic lens, in particular for sunglasses

ABSTRACT

An ophthalmic lens comprising a substrate is provided with the lens having a transmission spectrum such that the mean transmission value in the wavelength range between 380 nm inclusive and 780 nm inclusive is less than 60%, the mean transmission value at wavelengths less than or equal to 400 nm is less than 1%, the mean transmission value at wavelengths greater than 400 nm inclusive and less than 500 nm inclusive is less than 30% with a transmission minimum of less than 10% between 425 nm and 445 nm inclusive and the mean transmission value in the wavelength range between 400 nm and 500 nm has a first transmission maximum located between 405 nm and 425 nm.

RELATED APPLICATION

This application claims priority to French application FR1550796 filedFeb. 2, 2015.

TECHNICAL FIELD

The present invention relates to an ophthalmic lens, in particular forsunglasses.

BACKGROUND

The wearing of sunglasses, in particular in very bright light, ismedically highly recommended for protecting long-term vision potentialand also for safety reasons, for example when driving.

Specifically, sunglasses form a barrier to UV rays. Many studies haveshown that UV rays may cause lesions, inflammations or deteriorations ofthe cornea, of the crystalline lens or of the retina. In order toprevent these effects and above all a modification of the eye which mayreduce long-term vision, people are increasingly encouraged to wearsunglasses to prevent exposure to a too high light intensity.

Furthermore, sunglasses also make it possible to combat glare, whichincreases safety when driving or during sporting activities.

This is why sunglasses generally sold today block any radiation having awavelength of less than 400 nm.

However, medical studies in recent years have shown that a wavelengthrange around 435 nm (±20 nm), also known under the name “bad bluelight”, plays an important role, for example in age-related maculardegeneration (AMD). This is a process which is cumulative over alifetime and which becomes troublesome in particular for people over 60years old.

In order to solve these problems, ophthalmic lenses are known that havefiltering properties in the visible blue part of the spectrum between400 nm and 480 nm.

However, these known ophthalmic lenses are not completely satisfactoryin so far as a portion of the “good blue light” between 450 nm and 480nm is also significantly attenuated, which is detrimental to the visualspectral perception of the sunglasses wearer. Furthermore, adeterioration of the contrast perceived by the user is observed, whichmay be a safety drawback, in particular for driving.

Documents U.S. Pat. No. 5,149,183, EP 2 602 655, FR 2 990 774, andUS2010/149483 relate to ophthalmic lenses belonging to the state of theart.

The objective of the invention is therefore to propose an improvedophthalmic lens that makes it possible to at least partially solve thedrawbacks of the prior art.

SUMMARY

For this purpose, one subject of the invention is an ophthalmic lenscomprising a substrate, said lens having a transmission spectrum suchthat:

-   -   the mean transmission in the wavelength range between 380 nm        inclusive and 780 nm inclusive (meaning within the wavelength        range [380 nm; 780 nm]) is less than 60%;    -   the mean transmission at wavelengths less than or equal to 400        nm is less than 1%, preferably less than 0.5%, very preferably        less than 0.1%;    -   the mean transmission at wavelengths greater than 400 nm        inclusive and less than 500 nm inclusive (meaning within the        wavelength range [400 nm; 500 nm]) is less than 30% with a        transmission minimum of less than 10%, preferably less than 5%,        very preferably less than 1% between 425 nm and 445 nm inclusive        (meaning within the wavelength range [425 nm; 445 nm]).

Owing to these properties, the ophthalmic lens according to theinvention is capable of filtering out the wavelengths corresponding toultraviolet light, but also the wavelengths corresponding to bad bluelight, with great effectiveness, and therefore of protecting thewearer's eye, while preserving the colorimetric characteristics of thelens. Indeed, although cutting out the bad blue light, the lens allows asufficient transmission of blue light, in particular with respect to thespectrum for perception of colour by the eye. Furthermore, it makes itpossible to have a glass with a colour comprising blueish shades sincenot all the blue light is cut out.

Finally, the ophthalmic lenses intended for sunglasses must meet certaincriteria relating to the perception of colours by the wearer. Inparticular, such lenses must comply with the ISO 12312-1: 2013 and/orANSI Z80.3-2001 standards which define criteria for the wearing thereofwithin the context of a vehicle driving activity. Thus the ophthalmiclenses for sunglasses should in particular not modify the perception ofthe colour of traffic signals.

The ophthalmic lenses according to the invention thus guarantee, byvirtue of their transmission spectrum, an excellent protection for awearer owing to the simultaneous combination of the following factors:

-   -   reduced transmission over the whole of the visible spectrum        owing to their solar characteristics,    -   absorption of the UV wavelengths,    -   very highly effective absorption of the bad blue light,    -   maintaining a transmission in the “good blue light” and    -   compliance with the ISO12312-1: 2013 and/or ANSI Z80.3-2001        standards thus offering safety when worn during a vehicle        driving activity.

The ophthalmic lens may have one or more of the following features:

The mean transmission in the wavelength range between 400 nm and 500 nmhas, for example, a first transmission maximum located between 405 nmand 425 nm.

According to one aspect, the first maximum located between 405 nm and425 nm is at least six times higher than the transmission of the firsttransmission minimum.

According to another aspect, the percentage of transmission of the firstmaximum is at least two times higher than the percentage of transmissionof the first minimum, the percentage of transmission of the firstmaximum having a percentage of transmission being at least the value oftransmission of the first transmission minimum increased by a percentagevalue of 2%.

According to a further aspect the first maximum is in percentage atleast 2%, preferentially 4% higher than the percentage of transmissionof the first minimum of transmission.

According to one aspect, the first minimum is located at 435 nm with anaccuracy of ±5 nm, preferably with an accuracy of ±2 nm.

According to another aspect, the first minimum is an absorption peakwith a degree of absorption of greater than 95% and preferably greaterthan 99.5%.

The absorption peak may have a quarter-height width of 50 nm or less,and a half-height width of 30 nm or less, and a width at two thirds ofthe height of the absorption peak of 20 nm or less.

According to yet another aspect, the transmission at the first maximumis greater than 1%, preferably greater than 4%.

According to another aspect, the transmission in the wavelength rangebetween 440 nm and 500 nm increases.

The mean transmission between 380 and 780 nm inclusive may be less than35%, in particular less than 25% and preferably less than 18%.

The mean transmission between 400 nm and 450 nm is, for example, lessthan the mean transmission between 450 nm and 650 nm and the meantransmission between 450 nm and 650 nm is, for example, less than themean transmission between 650 nm and 780 nm.

According to another aspect, the ophthalmic lens is suitable for drivingaccording to the ISO 12312-1: 2013 standard.

The ophthalmic lens may comprise a polarizing assembly.

The substrate comprises, for example, a thermoplastic material, inparticular polycarbonate.

The invention also relates to a process for optimizing a colour of anophthalmic lens with a view to conformity with the ISO 12312-1: 2013standard relative to a given spectrum, in which the transmission of thelens in the range between 405 nm and 425 nm on the one hand and between440 nm and 450 nm on the other hand is increased and the transmission inthe wavelength range between 430 nm and 440 nm is decreased.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will appear more clearlyon reading the following description, given by way of illustrative andnon-limiting example, and from the appended drawings showing:

FIG. 1 is an example of an ophthalmic lens according to the invention,

FIG. 2 is a graph showing the transmittance of a first example of anembodiment of an ophthalmic lens according to the invention as afunction of the wavelength,

FIG. 3 is a graph showing the transmittance of a second example of anembodiment of an ophthalmic lens according to the invention as afunction of the wavelength,

FIG. 4 is a graph showing a comparative example of the transmittance ofan ophthalmic lens according to the state of the art as a function ofthe wavelength, and

FIG. 5 is a graph showing the transmittance of a third example of anembodiment of an ophthalmic lens as a function of the wavelength.

On all the figures, identical elements bear the same reference numbers.

DETAILED DESCRIPTION

An example of an embodiment will now be described with reference to thefigures.

The following embodiments are examples. Although the description refersto one or more embodiments, this does not necessarily mean that eachreference relates to the same embodiment, or that the features applyonly to a single embodiment. Simple features of various embodiments mayalso be combined and/or interchanged to provide other embodiments.

For the mean transmission between two wavelengths λ₁ and λ₂, the ISO11664-1 and ISO 11664-2 definitions are, for example, taken intoaccount.

More specifically, the mean transmission may be defined as:

$\tau_{v} = {100 \times \frac{\int_{\lambda\; 1}^{\lambda\; 2}{{\tau(\lambda)}{S_{D\; 65}(\lambda)}{V(\lambda)}d\;\lambda}}{\int_{\lambda\; 1}^{\lambda\; 2}{{\tau(\lambda)}{S_{D\; 65}(\lambda)}{V(\lambda)}d\;\lambda}}}$

where

λ is the wavelength in nanometers,

τ(λ) is the spectral transmittance of the lens,

V(λ) is the spectral luminous efficiency function for vision,

S_(D65)(λ) is the spectral distribution according to the CIE standard(see ISO 11664-2).

In the present description, the expression «inclusive» is meant toinclude also the limits or borders that will also belong to thedesignated range. For example a wavelength between «425 nm and 445 nminclusive», it is meant that the wavelength range also comprises theborder values ([425 nm, 445 nm]). In this way, it is defined awavelength range from a wavelength superior or equal to 425 nm up toinferior or equal to 445 nm.

FIG. 1 is a schematic cross-sectional view of an exemplary embodiment ofan ophthalmic lens 1 according to the invention.

This ophthalmic lens 1 is tinted and is for example intended to be usedfor spectacles, in particular sunglasses. For this, it is only necessaryto shape the outer edge 3 to the desired shape of the rim of the frame.

An ophthalmic lens is understood to mean a finished or semi-finishedcorrective or non-corrective lens, capable of being mounted in a frame,for example a spectacle frame, a mask and a visor.

The solar ophthalmic lens may or may not be tinted, or may have a tintgradient, and it may comprise other solar functions such as a polarizingor photochromic function, alone or in combination.

It may also comprise other additional functions, alone or incombination, from the following non-exhaustive list: impact-resistant,scratch-resistant, abrasion-resistant, anti-reflective, mirror,anti-soiling, anti-fogging and antistatic functions. These additionalfunctions may be produced according to conventional methods (dipcoating, vacuum deposition, spin coating, spray coating, etc.).

-   -   The tinted ophthalmic lens 1 comprises, for example, a        polarizing assembly 5 composed of at least one first layer 7 and        one second layer 9 of a thermoplastic or thermosetting material        sandwiching a polarizing film 11. Of course, this polarizing        assembly 5 with its layers 7, 9 and 11 is optically transparent,        that is to say that it lets light pass through.    -   As can be seen in FIG. 1, the ophthalmic lens 1 additionally        comprises at least one third layer forming a substrate 13 of a        thermoplastic material, for example made of polycarbonate, which        is transparent, tinted or coloured, adhering by injection        moulding to the second layer 9.    -   By way of example, the polarizing assembly 5 has a thickness e1        of between 0.3 and 1 mm and the third layer forming a substrate        13 has a thickness e2 of between 0.5 and 2 mm.    -   The polarizing film is, for example, a film of polyvinyl alcohol        (PVA) known for its polarizing properties.    -   For a glasses use, the layer 13 will be the one intended to be        closest to the user's eye and the layer 7 will be the one        furthest from the user's eye.    -   As mentioned above, the two layers 7, 9 may be made of a        thermoplastic or thermosetting material, and the layer 13 may be        made of a thermoplastic material.    -   As a thermoplastic material, it is possible, for example, to        choose from the following group: polymethyl (meth)acrylate,        polycarbonate, polycarbonate/polyester blends, polyamide,        polyester, cyclic olefin copolymers, polyurethane, polysulphone,        TAC (cellulose triacetate) and a combination thereof.    -   As thermosetting material, it is possible, for example, to use a        transparent material such as CAB (cellulose acetate butyrate).    -   In order to colour the thermoplastic material, it is possible to        add pigments or colourants. These may be organic or mineral        pigments. Among these, there is in particular the pigment sold        under the reference ABS549 by EXCITON (registered trademark)        which is a specific absorber of narrow wavelength width.

In the present case, the substrate formed by the layer 13 comprisesseveral colourants, especially ABS549, which cooperate together in orderto absorb the light passing through the lens, the lens having atransmission spectrum such that, as is seen in FIGS. 2 and 3 that showtwo examples of spectra, one for a glass of grey colour when seen by anexternal observer (FIG. 2) and the other for a glass of brown colourwhen seen by an external observer (FIG. 3):

-   -   the mean transmission in the wavelength range between 380 nm        inclusive and 780 nm inclusive is less than 60%;    -   the mean transmission at wavelengths less than or equal to 400        nm is less than 1%, preferably less than 0.5%, very preferably        less than 0.1%;    -   the mean transmission at wavelengths greater than 400 nm        inclusive and less than 500 nm inclusive is less than 30% with a        transmission minimum denoted by the reference 100 of less than        10%, preferably less than 5%, very preferably less than 1%        between 425 nm and 445 nm inclusive.

Furthermore, the transmission at wavelengths between 405 nm and 425 nmwhich is non-zero has a first transmission maximum denoted by thereference 105 which is at least 100% greater than the transmission atthe first transmission minimum 100.

The first maximum 105 is at least six times greater than thetransmission of the first transmission minimum 100.

The transmission at the first minimum 100 is less than 5%, preferablyless than 0.5% (for the version of the spectrum from FIG. 3).

The first minimum 100 is an absorption peak with a degree of absorptionof greater than 95% and preferably greater than 99.5%.

In greater detail, the absorption peak 100 has a quarter-height width of50 nm or less, and a half-height width of 30 nm or less, and a width attwo thirds of the height of the absorption peak 100 of 20 nm or less.

The half-height is found at the location where the absorption is halfthe maximum absorption. The quarter-height is found at the locationwhere the absorption is a quarter of the maximum absorption. Thetwo-thirds height is found at the location where the absorption is twothirds of the maximum absorption.

The first minimum 100 is located at 435 nm with an accuracy of ±5 nm,preferably with an accuracy of ±2 nm. It is therefore seen that the badblue light is indeed filtered by the lens 1 according to the inventionwhile transmitting at least one portion of the blue wavelengths of thevisible light spectrum, which is not harmful for the human eye and cantherefore be used for safe vision. It is therefore understood that inthis way a lens is obtained that gives better eye protection whileresulting in only a small, reduced and in some cases nearlyimperceptible deformation of the perception of contrasts and colours.

The transmission at the first maximum 105 is greater than 1%, preferablygreater than 4%.

The transmission in the wavelength range between 440 nm and 500 nmincreases in particular for the “brown” version from FIG. 3.

Depending on the sunglasses category, the mean transmission between 380and 780 nm inclusive is less than 35%, in particular less than 25% forcategory 2 and preferably less than 18% for category 3.

For the two examples from FIGS. 2 and 3, the mean transmission between400 nm and 450 nm is less than the mean transmission between 450 nm and650 nm and the mean transmission between 450 nm and 650 nm is less thanthe mean transmission between 650 nm and 780 nm.

As regards the “brown” version from FIG. 3, the mean transmissionbetween 400 nm and 500 nm is less than the mean transmission between 500nm and 650 nm and the mean transmission between 500 nm and 650 nm isless than the mean transmission between 650 nm and 780 nm.

As from the colorimetry point of view, the colorimetric characteristicsof the colorimetric CIE model may be the following: L between 36.0 and37.0, in particular 36.83, a between 6.0 and 7.5, in particular 6.91,and b between 18.0 and 19.5, in particular 18.95.

Furthermore, the ophthalmic lens is thus suitable for driving accordingto the ISO 12312-1: 2013 standard.

FIG. 4 shows as an example the transmittance of an ophthalmic lensaccording to the state of the art as a function of the wavelength. Thislens is of brown colour when seen by an external observer. Themeasurements of the features of this lens have shown that this lens isnot suitable for driving.

However, one may proceed thanks to the invention to an optimization ofthe colour of such an ophthalmic lens in view of its conformity to theISO 12312-1: 2013 with respect to the spectrum given in FIG. 4 forexample, by increasing, with respect to the reference curve for examplein FIG. 4 the transmission of the lens in the wavelength ranges locatedbetween 405 nm et 425 nm on the one hand and between 440 nm et 450 nm onthe other hand, and in decreasing the transmission in the wavelengthrange located between 430 nm et 440 nm.

One may get in this way a lens having a transmittance curve asrepresented in FIG. 5 which shows a graph showing the transmittance of athird example of an embodiment of an ophthalmic lens as a function ofthe wavelength. The measurements of the features of this lens have shownthat this lens is suitable for driving and this without that theperception of the colour of the tinted lens by an external observer haschanged.

It is therefore clearly understood that the ophthalmic lenses accordingto the invention make it possible to protect the human eye moreeffectively against bad blue light without the non-harmful portion ofthe blue light being excessively attenuated.

It is in particular possible to observe in FIGS. 2, 3 and 5 that thetransmission in the wavelength range between 400 nm and 500 nm presentsa first transmission maximum 105 located between 405 nm and 425 nm thatshows

-   -   to be at least six times higher than the transmission of the        first transmission minimum 100, or    -   to have a percentage of transmission that is at least two times        higher than the percentage of transmission of the first minimum        100, the percentage of transmission of the first maximum 105        having a percentage of transmission being at least the value of        transmission of the first transmission minimum increased by a        percentage value of 2%, or    -   to be in percentage at least 2%, preferentially 4% higher than        the percentage of transmission of the first minimum of        transmission 100.

By the condition that the percentage of transmission of the firstmaximum 105 is at least two times higher than the percentage oftransmission of the first minimum 100, the percentage of transmission ofthe first maximum 105 having a percentage of transmission being at leastthe value of transmission of the first transmission minimum increased bya percentage value of 2%, it is meant that if T_(min1) is the value oftransmittance of the first transmission minimum 100 and T_(max1) is thevalue of transmission of the first transmission maximum 105,T_(max1)>2*T_(min1) et T_(max1)>T_(min1)+2%.

By the condition, that the percentage of the first maximum 105 is atleast 2%, preferentially 4% higher than the percentage of transmissionof the first minimum of transmission 100, it is meant thatT_(max1)>T_(min1)+2%., in particular T_(max1)>T_(min1)+4%.

According to the example in FIG. 3, the first transmission minimum 100exhibits a transmission value of 0.44% and the first transmissionmaximum 105 of 4.48%.

In this case, the transmission the first transmission maximum 105 is10.2 times higher than the transmission of the first transmissionminimum 100.

The difference between the transmission of the first transmissionmaximum 105 and the first transmission minimum is 4.04% (=4.48%-0.44%)and thus the transmission of the first transmission maximum 105 is atleast two times higher than the percentage of transmission of the firstminimum 100, the percentage of transmission of the first maximum 105having a percentage of transmission being at least the value oftransmission of the first transmission minimum increased by a percentagevalue of 2% (in this case by 4.04%).

The percentage of the first maximum 105 is thus more than 4% higher thanthe percentage of transmission of the first minimum of transmission 100.

Other variants are possible without departing from the scope of thepresent invention. Thus, the substrate, the layer 13 may be shaped tofurthermore provide an optical correction to the vision of the user.

The layer 13 may be sandwiched between the polarizing assembly andanother layer, for example made of clear or coloured polycarbonate. Inthis case, it may be the latter layer which is cut/polished in order toprovide an optical correction and not the layer 13.

What is claimed is:
 1. Ophthalmic lens comprising a substrate, saidophthalmic lens having a transmission spectrum such that: a meantransmission value in the wavelength range between 380 nm inclusive and780 nm inclusive is less than 60%; a mean transmission value atwavelengths less than or equal to 400 nm is less than 1%; a meantransmission value at wavelengths greater than 400 nm inclusive and lessthan 500 nm inclusive is less than 30%, wherein a lowest transmissionvalue for a range of wavelengths greater than 410 nm inclusive and lessthan 500 nm inclusive occurs between 425 nm and 445 nm inclusive, andwherein the lowest transmission value has a transmittance of less thanor equal to 1%; and a mean transmission value in the wavelength rangebetween 400 nm and 500 nm has a first transmission maximum locatedbetween 405 nm and 425 nm.
 2. Ophthalmic lens according to claim 1,wherein the first maximum located between 405 nm and 425 nm is at leastsix times higher than the lowest transmission value.
 3. Ophthalmic lensaccording to claim 1, wherein the percentage of transmission of thefirst transmission maximum is at least two times higher than thepercentage of transmission of the lowest transmission value, thepercentage of transmission of the first transmission maximum having apercentage of transmission being at least the value of transmission ofthe lowest transmission value increased by a percentage value of 2%. 4.Ophthalmic lens according to claim 1, wherein the lowest transmissionvalue is located at 435 nm with an accuracy of ±5 nm.
 5. Ophthalmic lensaccording to claim 1, wherein the lowest transmission value is anabsorption peak with a degree of absorption of greater than 95%. 6.Ophthalmic lens according to claim 5, wherein the absorption peak has aquarter-height width of 50 nm or less, and a half-height width of 30 nmor less, and a width at two thirds of the height of the absorption peakof 20 nm or less.
 7. Ophthalmic lens according to claim 1, wherein thetransmission at the first transmission maximum is greater than 1%. 8.Ophthalmic lens according to claim 1, wherein the transmission in thewavelength range between 440 nm and 500 nm increases.
 9. Ophthalmic lensaccording to claim 1, wherein the mean transmission between 380 and 780nm inclusive is less than 35%.
 10. Ophthalmic lens according to claim 1,wherein the mean transmission between 400 nm and 450 nm is less than themean transmission between 450 nm and 650 nm and the mean transmissionbetween 450 nm and 650 nm is less than the mean transmission between 650nm and 780 nm.
 11. Ophthalmic lens according to claim 1, wherein itcomprises a polarizing assembly.
 12. Ophthalmic lens according to claim1, wherein the substrate comprises a thermoplastic material, inparticular polycarbonate.
 13. Ophthalmic lens according to claim 1,wherein the first transmission maximum is in percentage at least 2%higher than the percentage of transmission of the lowest transmissionvalue.
 14. Ophthalmic lens according to claim 1, wherein the lowesttransmission value for the range of wavelengths greater than 410 nminclusive and less than 500 nm inclusive occurs between 433 nm and 437nm inclusive.
 15. A process for optimizing a color of an ophthalmic lenscomprising: increasing a transmission value of ophthalmic lens in therange between 405 nm and 425 nm; decreasing the transmission value ofthe ophthalmic lens in the range between 430 nm and 440 nm, such that ina range of wavelengths greater than 410 nm inclusive and less than 500nm inclusive, there exists a lowest transmission value between 430 nmand 440 nm inclusive, and wherein the lowest transmission value has atransmittance of less than or equal to 1%; and increasing thetransmission value of the ophthalmic lens in the range between 440 nmand 450 nm.
 16. The process of claim 15, wherein the lowest transmissionvalue for the range of wavelengths greater than 410 nm inclusive andless than 500 nm inclusive occurs between 433 nm and 437 nm inclusive.